When should I really stop etching a white spot?
A clinical case by our Community member Dr. Alessandro Colella
Although they may be pre- or post-eruptive, all white defects of the enamel have one thing in common, which is a histological condition of hypomineralization. The reason why the human eye perceives a white spot lies in a variation of the Refractive Index (RI) of the hypomineralized enamel, in which the mineral phase is severely diminished and replaced by organic ﬂuids having a remarkably lower RI than that of sound enamel.
The appearance of white lesions depends on the physical behaviour of light. For optical reasons, when there is a diﬀerence in the refractive indexes (RI) between two phases, i.e. healthy and hypomineralized enamel, a deviation of incident light rays happens at the interface. At each interface, the light is deviated and reﬂected, staying trapped in an “optical labyrinth” that is over-luminous and therefore perceived as white.
Nowadays white discolorations may be treated in a minimally or non-invasive approach, by evening out the RI, while “touching” the tooth as little as possible. The main factors to take into consideration is the depth of the lesions and their position inside the thickness of the enamel.
This 25-years-old female patient came to my observation complaining about her smile because of some white spots. She never had an orthodontic treatment, and got some professional bleaching in the last four years. She asked that her white spots be treated in one single session, as she would have been attending her graduation ceremony three days later.
Photography and transillumination, even with a common curing light, are useful tools to better understand the depth of the defect and choose the right treatment plan. More precisely, when a white spot is crossed by light, meaning the light isn’t stopped at all by it, a micro-invasive restorative treatment can be performed predictably.
In this particularly case I chose to treat the patient with a resin inﬁltration technique (Icon – DMG Germany). Rubber dam isolation is highly recommended, and it was performed in order to have a dry and more comfortable working space, tissue protection, and acceptable retraction.
After having properly cleaned tooth surfaces, an a 15% chlorhydric acid etching solution (Icon-Etch -DMG Germany) was applied on the involved teeth and rubbed for 2 minutes, with the aim of getting easier access to the hypomineralization. The acidic gel was then rinsed thoroughly and teeth air-dried.
An ethanol solution (Icon Dry – DMG Germany) is used to perfectly dry the surface. This solution has a refractive index very similar to resin’s one, so it also allows to get a preview of the ﬁnal outcome. Abundant ethanol is applied and left for at least 30 seconds to allow a better penetration and provide a more reliable previsualization.
This step is crucial because, depending on the result, we decide whether to repeat the process, or start the resin inﬁltration. In this speciﬁc case, I decided to repeat the acid application.
Even the result after the third ethanol application, although close to the expectation, was not fully satisfactory, so a fourth, and last, etching step was required.
I was pleased with this achievement and I decided, therefore, to inﬁltrate the spots.
A low viscosity, solvent-free resin (Icon Inﬁltrant – DMG Germany) is able to penetrate as much as the previously used ethanol solution. Resin inﬁltration requires 3 minutes application, and rubbing on the tooth surface with a speciﬁc tip. Let the resin act to a proper capillary eﬀect.
I ﬂossed to remove the excess and separate teeth not to splint them after light curing.
Each tooth was polymerized for 40 seconds. This inﬁltrant step was repeated, letting the inﬁltrant set again for 1 minute before light curing for another 40 seconds.
Another critical step is the polishing procedure. Rough resin on the surface is extremely sensitive to the oral environment and staining, so polishing steps are mandatory for the ﬁnal aspect and long term stability. Here’s the ﬁrst silicone tip used.
A second silicone tip with a ﬁner grit.
Final step: a goat brush with an extra-ﬁne diamond paste, using low pressure and low rotation.
Finally the surfaces were polished.
Right after rubber dam removal. The patient is really happy about the result.
At recall, 3 months later, integration is very good.
The smile 3 months after the treatment.
Before and after.
Maximal outcome with minimal intervention was achieved. The resin inﬁltration technique can be our ﬁrst choice when white discolorations are conﬁned in the outer portion of the enamel. Fluorosis (mainly TSIF I, II and III) and white spots due to caries, therefore, are the main indicated hypomineralization to be treated with ICON.
Sometimes more than two etching steps are required to solve the problem. Follow the feedback given from ethanol solution, and remember to let it sit on the surface for at least 30 seconds for a predictable, and reliable preview. Ethanol easily evaporates, but, if the etching step was eﬀective, the preview would last longer. Don’t forget to properly polish because it’s a crucial step for the long-term success.
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